Low-pressure absorption refrigerating system



J. G. REID, JR 2,473,389

LOW-PRESSURE ABSORPTION REFRIGERATING SYSTEM June 14, 1949.

Filed. Jan. 2, 1947 I 74 INVENTOR- @ATTQRNEY Patented June 14, 1949 LOW-PRESSURE ABSORPTION REFRIGERATING SYSTEM John G. Reid, Jr., Evansville,

Ind., assignor to Servel, Inc., New York, N. Y., a corporation of Delaware Application January 2, 1947, Serial No. 719,871

6 Claims. 1

The present invention relates to refrigeration systems and more particularly to apparatus for sealing the shaft of a liquid circulating pump in such a system to prevent air from entering the system.

While the present invention may have other applications it is particularly adapted for use with an absorption refrigeration system of the type illustrated and described in the application for United States Letters Patent of Albert R. Thomas,

Serial No. 560,214, filed October 25, 1944, and entitled-Refrigeration. Such a system has an internal pressure considerably below atmospheric pressure and utilizes water as a refrigerant and a salt solution as an absorbent. Refrigerant in the evaporator is circulated through a cooling element at a place remote from the evaporator by a circulating pump and absorption solution is recirculated in the absorber by another circulating pump. The pumps are operated intermittently in response to a demand for refrigeration as controlled by a thermal responsive element or other suitable control. Due to the low pressure in the system, air is apt to leak into the system around the pump shafts and such air blankets the heat transfer surfaces which it covers and prevents the transfer of heat.

One of the objects of the present invention is to provide an apparatus in a vacuum type absorption refrigeration system which utilizes liquid delivered by a circulating pump in the system for sealing the pump shaft to prevent air from entering the system.

Another object is to provide an apparatus of the type indicated for supplying liquid to the shaft housing of the pump at a pressure greater than atmospheric pressure.

Still another object is to provide an apparatus of the type indicated for maintaining the liquid seal in the shaft housing between periods of operation of the circulating pump.

These and other objects will become more apparent from the following description and drawing. It is to be expressly understood, however, that the drawing is for the purpose of illustration only and not a definition of the limits of the invention, reference being bad for thispurpose to the appended claims.

In the drawing:,

Fig. 1 is a diagrammaticview of an absorption refrigeration system incorporating the shaft sealing apparatus of the present invention, and

Fig. 2 is an enlarged part sectional View of a pump shaft and housing and showing the liquid chamber therebetween for sealing the shaft.

The present invention is shown in the drawing as applied to an absorption refrigeration system of the type illustrated and described in the Thomas patent referred to above. The refrigeration system comprises a generator 5, condenser 6, evaporator 1, absorber 8 and liquid heat exchanger 9, interconnected to provide paths for the circulation of refrigerant and absorbent. The generator 5 comprises a plurality of upright tubes In connected'at their lower ends to an inlet chamber II and at their upper ends to a separating chamber 12 having baflies I 3 therein. Surrounding the upright tubes I0 is a shell or jacket l4 providing a heating chamber l5 therebetween. Steam is supplied to the heating chamber Hi from any suitable source through a conduit I6 and the amount of steam supplied may be controlled by a valve I'l operated by a suitable electric motor 18. The heating chamber I5 is maintained at atmospheric pressure by means of a vent pipe I9 and condensate drains from the chamber through a return pipe 20. Refrigerant vapor flows from the separating chamber [2 of the generator 5 to the condenser 6 through a connecting conduit 23'.

The condenser 6 comprises a casing forming a chamber'for receiving refrigerant vapor and a plurality of tubes 24 extending longitudinally of the chamber and through which cooling water flows to condense the refrigerant vapor in the chamber. Condensed liquid refrigerantv flows from a sump 25 at the bottom of the condenser through a U-shaped tube or trap 26 into the evaporator l. r

The evaporator l is in the form of a horizontally arranged cylindrical tank and the end of the U-shaped tube 26 extends upwardly through its bottom. Liquid refrigerant in the evaporator is circulated through a heat exchanger or cooling element 27 in an auxiliary loop circuit connected to the evaporator. The auxiliary loop circuit comprises a conduit 28, circulating pump 29,

conduit 30, the heat exchanger or cooling element 21 and conduit 3|. The end 32 of the conduit 3| extends horizontally into the evaporator I adjacent the top thereof and has a series of perforations 33 for spraying the refrigerant into the evaporator to promote evaporation therein. A stand-pipe and overflow pipe 35 project upw'ardly from the absorber 8 through the bottom of the evaporator to different heights therein. Refrigerant vapor in the evaporator l flows through the open end of the stand-pipe 34 into the absorber 8 and a baffle'36 is provided between the end of the spray pipe 32 and the stand-pipe to auasac prevent the flow of liquid refrigerant with the refrigerant vapor.

The absorber 8 is also in the form of a horizontally arranged cylindrical vessel positioned below the evaporator I and has banks of cooling coils 38 therein. Absorption solution in the absorber 8 is recirculated in an auxiliary circuit including a conduit 38, circulating pump 48, conduit 4|, and spray pipe 42 extending longitudinally into the absorber adjacent the top thereof and having a series of spray nozzles 43.

Absorption solution weak in refrigerant or, in other words, concentrated salt solution flows by gravity from the separating chamber I2 of the generator 5 to the top of the absorber 8 in a path of flow including the conduit 44, heat exchanger 8 and conduit 45, the end of the latter extending horizontally into the absorber 8 and having a series of perforations 48 for spraying the solution into the absorber. Absorption solution strong in refrigerant or, in other words, dilute salt solution is delivered from the absorber 8 to the inlet chamber I I at the base ofthe generator 5 through a path of flow including a conduit 41 connected to the conduit 4| of the auxiliary circuit, liquid heat exchanger 8 and conduit 48.

Cooling water from any suitable source, such as a city main, cooling tower, or the like, is de; livered through a conduit 48 to a header 58 in the absorber 8 which distributes it for flow through the bank of coils 38. Cooling water is delivered from the bank of coils 38 to a header 5| and from the header it flows through a conduit 52 to the inlet chamber 53 at one end of the condenser E. The cooling water then flows through the tubes 24 in the condenser 5 and is discharged into an exhaust chamber 54 and waste pipe 55 as controlled by valve 55a.

The generator 5 and condenser 8 operate at a pressure corresponding to the vapor pressure of the refrigerant in the condenser and the evaporator I and absorber 8 operate at a lower pressure corresponding to the vapor pressure of the refrigerant in the evaporator. The difference in pressures in the two sides of the system is maintained by liquid columns in the conduits 28 and and by the pump 48 between the absorber 8 and generator 5.

The circulating pumps 28 and 48 are driven by electric motors 56 and 51, respectively, and the motors are electrically connected for simultaneous. operation in response to a demand for refrigeration. While any suitable control may be provided, as illustrated in the drawings, the electric motors 58 and 51 and steam valve motor 18 are connected in parallel in an electric circuit 58, 58 controlled by a thermostatic switch 68 responsive to a temperature effected by the cooling element 21. As thus far described the refrigeration system is substantially identical with that illustrated and described in the Thomas application referred to above. I i

In accordance with the present invention apparatus is provided for positively sealing the shafts of the pumps 28 and 48 to prevent air from entering the system. The pumps 28 and 48 are of identical construction comprising a pump housing 18, a shaft H and a shaft housing 12 comprising a stufling box or seal having an annular chamber 73 surrounding the shaft,

see Fig. 2. While other types'of pumps havin 'a shaft housing with an annular chamber 13 may be used, a centrifugal pump is illustrated in the drawings comprising the shaft II and an im-- peller 14 mounted at'its end for rotation in the pump housing 18. The shafts II of the Pump 28 and 48 are Journaled in suitable thrust bearings in the motors 58 and 81.

As illustrated in detail in Fig. 2 the shaft 'II has a sleeve 15 mounted thereon with its inner end sealed by a packing 18 between it and the hub of the impeller I4. Surrounding the sleeve 15 are sealing rings 11 and I8 mounted and sealed by packing in the shaft housing 18 adjacent the impeller I4 and in a cap I8 at the outer end of the shaft housing, respectively. The cap I8 is detachably connected to the end of the shaft housing 12 by bolts .88 and a suitable packing 8| is clamped therebetween. An adjustable packing is mounted on the shaft sleeve 15 for rotation therewith and comprises forward and rearward holders 82 and 83 with an axial compression spring 84 therebetween. Each holder 82 and 83 mounts a packing ring 85 which bears against a side face of the sealing ring 11 or 18 and a packing ring 88 which surrounds and forms a seal with the sleeve 15. It will be observed that the construction described above comprising the packing rings 85 cooperating with the sealing rings I1 and 18, respectively, and the packing rings 88 cooperating with the sleeve 15 provide inner and outer. seals between the shaft II and shaft housing 12 at opposite ends of the chamber 13.

To positively seal the packing rings 85 and 85 the chamber 13 is filled with refrigerant, water, delivered from the pump 28. As illustrated in Fig. 1 a restriction 88 is provided in the conduit 38 of the auxiliary refrigerant circuit adjacent the pump 28 to cause the pump to deliver liquid at a pressure greater than atmospheric pressure. The relatively high pressure refrigerant is delivered from the conduit 38 to the chambers 13 in the housings I2 of the pumps 28 and 48 in a path of flow including conduit 88, check valve 88, conduit 8| and a conduit 82 connecting the inlet ports 83, see Fig. 2, of the shaft housings. An expansion chamber 84 is connected to the conduit 8| and contains air or other gas which is compressed by the liquid to maintain'a uniform constantly acting pressure on the liquid in the chamber 13 of the pump housings 12. A sight glass 85 may be provided at the side of the expansion chamber 84 to show the liquid level in the chamber and a valve connection 88 also is provided for introducing air or other gas into the chamber.

During operation of the pump 28 a portion of the liquid refrigerant delivered therefrom will flow from the conduit 38 into the chambers 13 of the pumps 28 and 48 and, being at a greater pressure than atmospheric pressure, will tend to flow between the packing rings 85 and the sealing rings l1, l8 and between the packing rings 88 and shaft sleeve 15 to positively seal the shaft and lubricate the contacting surfaces. When the circulating pump 28 is stopped the liquid in the conduit 8! will have a greater pressure than the liquid in the conduit 38 and close the check valve 88. The expansion chamber 84 will then maintain the refrigerant in the chambers 13 of the pump housings I2 at a pressure greater than atmospheric pressure to seal the packing rings and prevent air from entering the system. It will therefore be observed that the apparatus of the present invention operates to seal the pump shafts ll during periods of operation of the circulating pump 28 and also between periods of operation. One form of the invention having now circuit 58, 59, the steam valve I1 is opened to supply steam to the heating chamber |5 of the generator 5 and the pumps 29 and 49 operated to circulate refrigerant and absorbent. With steam supplied to the heating chamber I5 of the generator 5, heat is transmitted through the tubes In toexpel refrigerant, water, from the absorption solution therein. As the refrigerant vapor is expelled in the tubes l9 it rises and lifts the absorption solution into the separating chamber |2 by a climbing film action. Refrigerant vapor flows from the separating chamber |2 through the conduit 23 to the condenser 6 where it is cooled and condensed to a liquid by the cooling water in the tubes 24 and the liquid refrigerant flows through the U-shaped tube 26 into the evaporator The liquid refrigerant delivered to the evaporator is circulated through the cooling element 27 in the auxiliary circuit by the pump 29 and delivered back to the evaporator through the spray pipe 32. Evaporation of a portion of the refrigerant in the evaporator 1 reduces the temperature of the remaining refrigerant which, in turn, absorbs heat from the ambient in the cooling element 21. The refrigerant vapor flows from the evaporator I through the stand-pipe 34 into the absorber 8 and is absorbed in the absorption solution therein to produce a relatively low vapor pressure and evaporation temperature in the evaporator which is maintained by liquid columns in the conduits 26 and 45.

Absorption solution in the separating chamber |2 flows by gravity through the conduit 44, liquid heat exchanger 9, conduit 45 and spray pipe 46 into the absorber 8 where it is sprayed over the bank of cooling coils 38 in the absorber 8. Absorption solution in the absorber 8 is also recircu lated in the auxiliary loop circuit including conduit 39, pump 40, conduit 4| and spray pipe 42. A portion of the recirculated absorption solution is delivered to the inlet chamber ll of the generator 5 in a path of flow through the conduit 41, heat exchanger 9 and conduit 48.

' The liquid refrigerant is delivered from the pump 29 to the conduit 30 at a pressure greater than atmospheric pressure due to the restricting orifice 88 in the conduit 39. A portion of the relatively high pressure refrigerant from the pump 26 is delivered to the chambers '73 in the shaft of the system which is considerably below atmospheric pressure. The pressure it. the expansion chamber 94 and conduits 9| and 92 being greater than the pressure in the rest of the system closes the check valve 99 and traps the liquid in the chamber 94 at a pressure greater than atmospheric pressure. The liquid trapped in the chambers 13 of the shaft housings l2 continues to maintain the liquid seals on the shafts After the conduits 9| and 92, the shaft housing chambers l3 and the pressure chamber 94 have once been filled with liquid refrigerant, the expansion chamber operates to maintain a uniform constant pressure on the liquid in the shaft housing chambers and the check valve operates intermittently to supply additional refrigerant to maintain the pressure in the expansion chamber. Thus the shaft sealing apparatus of the present invention is effective both during operation of the pump 29 and between periods of operation to maintain a liquid seal in the shaft housings 12 of the pumps 29 to 40 to positively prevent air from entering the system.

- It will no be observed that the present invention provides an apparatus utilizing liquid delivered by a circulating pump in the system for sealing the pump shaft to prevent air from entering the system. It will further be observed that the apparatus maintains a liquid seal in the shaft housing at a pressure greater than atmospheric pressure and that the liquid seal is maintained between periods of operation as well as during operation housings 12 of the pumps 29 and 49 in a path of flow including the conduit 89, check valve 90 and conduits 9| and 92. The liquid refrigerant delivered by the pump 29 also enters the expansion chamber 95 and compresses the gas therein. As the refrigerant is delivered at a pressure greater than atmospheric pressure it will tend to leak out of the shaft housings 12 and into the pump housings 10 or to the atmosphere whereby to seal the shaft against the flow of air into the system.

After a period of operation the temperature of the ambient to be cooled is lowered by the transfer of its heat to the refrigerant and the thermostatic switch opens the electric circuit 58, 59 whereby the steam valve H is closed and the circulating pumps 29 and 40 are stopped. Immediately upon stopping of the pump 29 the pressure in the conduit 30 assumes the pressure in the rest of the pump. It will still further be observed that the present invention provides a relatively simple and compact apparatus which is effective in performing its intended function. V

While a single embodiment of the invention is herein illustrated and described it will be under stood that modifications may be made in construetion and arrangement of elements without departing from the spirit or scope of the invention. For example, other forms of stuffing boxes may be provided and absorption liquid instead of refrigerant can be used although the refrigerant,

; water, is preferred. Therefore, without limiting myself in this respect, the invention is defined by the following claims.

I claim:

1. In a vacuum type refrigeration system having a plurality of interconnected elements to provide a-circuit for refrigerant, a pump for clrculating liquid in said system and so constructed and arranged as to deliver the liquid at a pressure greater than atmospheric pressure, said pump having a-shaft extending out of said system and a housing surrounding the shaft, connecting means for supplying liquid delivered from said pump to said shaft housing, control mechanism for operating the pump periodically, and structure in said connecting means comprising a check valve for maintaining the liquid in said shaft housing ata pressure greater than the atmospheric pressure between periods of operation whereby to seal the shaft to prevent air from entering the system.

2. In a vacuum type refrigeration system having a plurality of interconnected elements to provide a circuit for refrigerant, a pump for circulating liquid in said system, said pump having a shaft extending out of said system and a housing surrounding the shaft, structure for resisting the flow of liquid delivered from said pump to produce a pressure adjacent the pump greater than atmospheric pressure, connecting means for supplying liquid delivered from said pump to said shaft housing at a pressure greater than atmospheric system having a plurality of elements interconnected to provide circuits for the circulation of a refrigerant and an absorbent, an auxiliary circuit including a pump for circulating refrigerant in the system, said pump having a shaft extending out of said system and a housing surrounding the shaft, a restriction in the auxiliary circuit for resisting the flow of refrigerant delivered from said pump to produce a pressure adjacent the pump greater than atmospheric pressure, packing between the shaft and housing of the pump having contacting surfaces, and connecting means for delivering refrigerant from'said pump to the shaft housing at a pressure greater than atmospheric pressure to seal the contacting surfaces of the packing.

4. In an absorption refrigeration system of the type which operates at a pressure below atmospheric pressure and utilizes water as a refrigerant and a salt solution as an absorbent, a generator, a condenser, an evaporator, an absorber, conduits interconnecting the elements to provide circuits for the circulation of the refrigerant and absorbent, an auxiliary circuit including a pump for circulating liquid refrigerant in the evaporator, said pump having a shaft extending out of said system and a housing surrounding the shaft, a restriction in the auxiliary circuit for resisting the flow of refrigerant delivered from said pump to produce a pressure adjacent said pump greater than atmospheric pressure, packing between the shaft and housing having contacting surfaces, means connecting the auxiliary circuit to the shaft housing, control mechanism for operating the pump periodically, and a check valve and expansion chamber in the connecting means to maintain liquid refrigerant in the housing at a pressure greater than atmospheric pressure between periods of operation whereby to seal the contacting surfaces of the packing in the housing.

5. In an absorption refrigeration system of the type which operates at a pressure below atmospheric pressure and utilizes water as a refrigerant and a salt solution as an absorbent, a generator, a condenser, an evaporator, an absorber,

conduits interconnecting the elements to provide circuits for the circulation of the refrigerant and absorbent, an auxiliary circuit including a pump for circulating liquid refrigerant in the evaporaton-a second auxiliary circuit includin a pump for circulating liquid absorbent in the absorber, each of said pumps having a shaft extending out of said system and a housing surrounding the shaft, a restriction in the flrst mentioned auxiliary circuit for resisting the flow of refrigerant to produce a pressure adjacent the pump greater than atmospheric pressure, packing between the shaft and housing of each of said pumps, connections for supplying refrigerant from the first mentioned auxiliary circuit to the shaft housings of each of said pumps, control mechanism for operating the pumps periodically, and

a check valve and expansion chamber in said connecting means for maintaining the liquid refrigerant in said shaft housings at a pressure greater than atmospheric pressure between periods of operation whereby to seal the shafts to prevent air from entering the system.

6. In a vacuum type refrigeration system having a plurality of interconnected elements to provide a circuit for refrigerant, a pump for circulating fluid in said system and so constructed and arranged as to deliver the fluid at a pressure greater than atmospheric pressure, said pump having a shaft extending out of said system and a housing surrounding the shaft, connecting means for supplying fluid delivered from said pump to said shaft housing to maintain the fluid in said housing at a pressure greater than atmospheric pressure, control mechanism for operating the pump periodically, and structure in said connecting means comprising mechanism for-permitting the flow of fluid to said housing while preventing the flow of fluid from said housing to maintain the fluid therein at a pressure greater than atmospheric pressure between periods of operation whereby to seal the shaft to prevent air from entering the system.

JOHN G. REID, JR.

REFERENCES CITED The following referenlces are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 686,737 Josse Nov. 19, 1901 1,979,525 Baumann Nov. 6, 1934 2,143,637 Volmann Jan. 10, 1939 

